Performance issue when accessing a CRL file

Question

Hi,
In an application we receive sign and verify files(ordinary information files) as seperate processes. When signing files we do a check on the CRL of the signing certificate. Below are the steps in which the check is done:
1- Receive a file. Get its signing certificate from a repository.
2-save/cache the CRL file in a directory(we do check if the file already exists when creating). We have configured a time out period with which the CRL will be updated in case of modifications.
File file = new File(cacheDirSystem.getProperty("file.separator")+crlUrl(url));+
fs = new FileOutputStream(file);
X509CRL crl.writeTo(fs);
3-Get the CRL Distribution Point from the signing certificate and load the file that was saved to check with the Certificate Revocation Lists.
String as[] = getDistributionPointNameURIs((GeneralNames)dpName);
File file = new File(cacheDirSystem.getProperty("file.separator")+modifyUrl(as));+
lastModified=file.lastModified();
fstream = new FileInputStream(file);
crlObject.crl=new X509CRL(fstream);
When running signing processes with more than 150 files(the file size can go upto 2MB) over a period of time, the CRL is sometimes not found and InvalidCRLException is thrown. I think its some problem with accessing the CRL file concurrently since it could also be updated at some point.
Im trying to figure out if a file lock or some other way would help to reslove this. I need help/suggestions on this.
Thanks in advance

Answer 1

I think its some problem with accessing the CRL file concurrentlyUndoubtedly. You should write the new data to a new file and do a delete/rename operation. All clients should cope with not finding the CRL file by retrying a couple of times in case they tried between the delete and the rename.
This is a file handling question, or concurrency question, not really a security question.